Genesis of the Wutuogou Ag-Pb-Zn deposit in the Eastern Kunlun Orogenic Belt, NW China: Constraints from calcite U-Pb geochronology, mineral chemistry, and in-situ sulfur isotopes

Wang, Shuang, Li, WeiWei, Zhao, Xu, Huizenga, Jan Marten, Zhang, Xinming, Xu, Chongwen, Yu, Siqi, Li, Yanjun, and Wei, Junhao (2024) Genesis of the Wutuogou Ag-Pb-Zn deposit in the Eastern Kunlun Orogenic Belt, NW China: Constraints from calcite U-Pb geochronology, mineral chemistry, and in-situ sulfur isotopes. Ore Geology Reviews, 165. 105880.

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Abstract

The Wutuogou Ag-Pb-Zn deposit, a newly discovered vein-type deposit, is located in the Eastern Kunlun Orogenic Belt (EKOB), northwestern China. The vein-type Ag-Pb-Zn ore bodies are hosted in Middle Triassic granodiorite %). Three paragenetic stages have been recognized: quartz + pyrite (Py-1) + arsenopyrite (stage I), pyrite (Py-2) + sphalerite + chalcopyrite + tetrahedrite + quartz (substage II-1), galena + pyrargyrite + freibergite + freieslebenite + quartz + calcite (substage II-2), and quartz + calcite (stage III). Except for Ag-bearing minerals (pyrargyrite, freibergite, and freieslebenite), invisible silver is also present in pyrite (1.91–165 ppm), sphalerite (3.86–8806 ppm), and galena (up to 0.21 wt%). The calcite is closely associated with sulfides in substage II-2 and yields a U-Pb age of 210 ± 7 Ma (MSWD = 2.7), which represents the ore-forming age (lower limit). Py-1 displays higher As contents and lower Co contents than those of Py-2, indicating a decrease in temperature from stage I to stage II. In addition, the Fe/Zn mass ratios (0.025–0.075) of sphalerite estimate the fluid temperature for substage II-1 of 246–284 ◦C, whereas the Ag/(Ag + Cu) and Zn/(Zn + Fe) mole ratios of freibergite estimate the fluid temperature for substage II-2 of 140–270 ◦C, further indicating the decrease of temperature from stage I through substage II-1 to substage II-2. Mineral assemblages of pyrite-chalcopyrite-tetrahedrite in substage II-1 and Ag-sulfosalts in substage II-2 suggest a decrease in sulfur fugacity (fS2). Both the decrease in fS2 and cooling of the mineralizing fluids facilitate silver precipitation. The heterogeneous compositions of the freibergite and the Ag zonation in sphalerite (Sp-1) resulted from retrograde solid-state reactions that redistributed Ag through microscale exsolution. The δ34S values (+5.49 to +7.78 ‰) of the sulfides and the low Zn/Cd ratios (107–195) of sphalerite indicate a felsic magma source for the ore-forming materials. Therefore, we concluded that the Wutuogou Ag-Pb-Zn deposit corresponds to a medium- to low-temperature magmatic-hydrothermal deposit associated with Late Triassic magmatism in the Eastern Kunlun Orogenic Belt (EKOB).

Item ID: 81581
Item Type: Article (Research - C1)
ISSN: 1872-7360
Keywords: Calcite U-Pb age, Mineral chemistry, In-situ sulfur isotopes, Vein-type Ag-Pb-Zn deposit, Eastern Kunlun Orogenic Belt
Copyright Information: © 2024 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
Date Deposited: 14 Jan 2024 23:01
FoR Codes: 37 EARTH SCIENCES > 3703 Geochemistry > 370303 Isotope geochemistry @ 30%
37 EARTH SCIENCES > 3703 Geochemistry > 370399 Geochemistry not elsewhere classified @ 70%
SEO Codes: 28 EXPANDING KNOWLEDGE > 2801 Expanding knowledge > 280107 Expanding knowledge in the earth sciences @ 100%
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